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18. PARTS
REPLACEMENT
18.1 IMPORTANT:
Before commencing with any part replacement the appliance should be isolated from the electrical
supply and the gas service cock on the appliance closed.
18.1.1
All parts that are removed should be replaced and refitted in reverse order, ensuring correct seals are
made and wires are connected correctly.
18.1.2
Remove any debris from within the appliance.
18.1.3
When gas-carrying components are replaced the appliance must be tested for gas tightness.
18.1.4
On completion carry out a full functional test of all appliance components and ensure system controls
are operating correctly.
PART REPLACEMENTS MADE WITHOUT DRAINING THE SYSTEM
18.2 BURNER
INJECTOR
18.2.1
Refer to paragraph 17.5
18.2.2
Remove the gas pipe securing clip from venturi. See Figure 36.
18.2.3
Undo the gas pipe union from the gas valve.
18.2.4
Withdraw gas pipe from venturi.
18.2.5
Remove injector from gas pipe.
18.2.6
Replace and refit in reverse order.
18.2.7
Check the operation of the boiler. See Section 15.
18.3 BURNER
ASSEMBLY/VENTURI
18.3.1
Refer to paragraph 17.5
18.3.2
Remove the burner assembly. See paragraph 17.7.
18.3.3
To replace the venturi, remove the 4 screws and replace with new.
18.3.4
Inspect the ignition/detection electrode and check the electrode gaps.
18.3.5
Replace with new burner assembly.
18.3.6
Replace the sealing gasket around the burner.
19.3.7
Refit in reverse order.
19.3.8
Check the operation of the boiler. See Section 15.
18.4
FLOW & RETURN THERMISTOR SENSORS
19.4.1
Refer to paragraph 17.5
19.4.2
Unclip the thermistor sensor from the flow/return pipe and withdraw it from
the boiler.
19.4.3 Disconnect the electrical leads from the thermistors.
19.4.4 Reconnect the electrical leads to the new thermistors and re-assemble in
reverse order, ensuring that the thermistors are securely.
19.4.5
Check the operation of the boiler. See Section 15.
18.5 IGNITION/DETECTION
ELECTRODE
18.5.1
Refer to paragraph 17.5
18.5.2
Remove the burner. See paragraph 17.7.
18.5.3
Remove the 2 torx screws holding the ignition electrode to the combustion
chamber.
18.5.4
Remove the electrode.
18.5.5 Fit the new ignition electrode, using the new gasket supplied. Check
dimensions as shown.
18.5.6
Refit in reverse order.
18.5.7
Check the operation of the boiler. See Section 15
18.6 GAS
VALVE
19.6.1
Refer to paragraph 17.5
19.6.2
Unplug the electrical lead connection from the gas control valve, disconnect
the PDT tube.
19.6.3
Undo the union nut on the top of the gas control valve.
19.6.4 Undo the gas inlet pipe union underneath the cabinet to the gas control
valve.
19.6.5
Remove the 2 screws retaining the valve to the bracket and withdraw.
19.6.6
Fit the new gas control valve ensuring the two sealing washers are in place
and reconnect gas, electrical connection and PDT tube.
19.6.7
Check operation of the boiler. See Section 15.
FIGURE 38. ELECTRODE GAP
FIGURE 39. GAS VALVE
FIGURE 37. THERMISTOR SENSOR
FIGURE 36. BURNER INJECTOR
CLIP
INJECTOR
‘O’ RING
3.5mm ±1
